equatorial mount diagram

Manual Equatorial Mounts. In terms of astrophotography, the telescope and additional accessories such as camera gear must be balanced and organized. The polar axis of an equatorial telescope mount must be pointed towards the north celestial pole, which is the point in the sky at which all of the stars appear to rotate around. Use a compass to adjust your mount away from magnetic north accordingly. This is essentially what deep sky astrophotography is all about, and almost every other aspect is geared towards improving this tracking accuracy with techniques such as autoguiding. A mount like this is extremely affordable and can carry a small telescope of up to 7 lbs. Because the RA coordinates are fixed on the celestial sphere, the RA disc can be driven using a clock drive running in sidereal time. For telescope observers and astrophotographers, this presents a challenge in terms of staying “locked on” a target. Take some stiff card and mark out a right-angled triangle that has one angle equal to your latitude. Putting your telescope on an equatorial mount allows you to follow stars as they continue their steady progress across the night sky. You just have to rotate the telescope’s other axis – the declination axis – to stay on target. If you ever photographed the night sky, you are probably aware of an effect called star trailing (which can be annoying, but can also be used to create fantastic photos).. Photo by Caleb Woods on Unsplash. You can find out the magnetic variance of your location using the British Geological Survey’s snappily named ‘Grid Magnetic Angle Calculator’. Tools like the QHY PoleMaster electronic polar finder offers a convenient way to fine tune these adjustments. The internal motors allow the telescope mount to rotate at sidereal rate, (or “clock drive“) and match the exact speed of Earth’s rotation. The next step is to set it to true north, which can be several degrees east of magnetic north from the UK. Today’s equatorial telescope mounts often use digital setting circles, consisting of two rotary encoders in both axis. Diagram of telescope types and mounts. I anticipate many aspiring amateur astrophotographers will quickly outgrow a non-motorized equatorial mount. The right ascension axis (RA), rotates in one revolution every (approximately) 24 hours. Plate solving has several advantages over a manual star alignment routine, such as the ability to match an existing object framing from a previous imaging session or meridian flip. Hold it against your mount, with the longest side against the polar axis, and place a spirit level on the shortest side – which should be uppermost. With a computerized mount that is able to track the motion of the stars, the telescope you attach to it is up to you. The Alt-Az mount was designed for convenience and practicality, at the cost of precision tracking over long periods of time. For example, with a non-tracking telescope mount such as a traditional Dobsonian design, objects at high magnification appear to gradually drift by in the eyepiece. The next logical step up from a manual EQ mount is one that includes a motorized clock drive, that allows you to take long-exposure photographs of deep sky objects in space. If the RA axis of the equatorial mount is not aligned with the celestial pole, it’s internal clock drive is not in sync with the rotation of the Earth. The declination axis is the side-to-side movement of the EQ mount, that provides the ability to point the telescope in any direction of the night sky. You can check the accuracy of your polar alignment on any clear night by loosening the polar axis clutch and steadily rotating the telescope around this axis. The alt-azimuth mount design simply allows you to move the telescope in altitude (up and down), and azimuth (left to right). This design allows the attached instrument (your camera or telescope) to stay fixed on a celestial object by driving one axis at a constant speed. If you ever seen the terms “right ascension” (RA), or “declination” (DEC) before, you might be scratching your head as to what these terms are referring to. Ninian Boyle is an astronomy educator. When observing solar system objects in space such as planets or the moon, this is not much of a problem as you can easily move the telescope slightly to ” keep up” with your subject. A payload that is too heavy on one side of either axis can result in poor tracking performance, and squander the effectiveness of autoguiding. There are a number of tools you can use to help polar align your equatorial mount, such as: Speaking of balance, the actual balancing of the weight on top of the mount (the payload) is extremely important. For example, the Orion EQ-1 equatorial telescope mount pictured below requires you to manually control the axis of the mount to stay on your target. Equatorial mounts can be a bit of a mystery if you’ve never used one before, but they don’t come much simpler than the EQ-1, which many small telescopes come with. Many equatorial mounts include a polar finder scope with an illuminated reticle, that provide you with a useful guide to to align the polar axis. Setting circles are used in an equatorial mount to find astronomical objects in the night sky by using their equatorial coordinates. Equatorial mounts usually include 1 or 2 counterweights as a package, depending on the payload capacity of the mount. As Earth rotates around this axis, the stars appear to move against the background sky over the course of the night, rising in the east and setting in the west. This method involves taking a picture of the night sky and identifying the star pattern from an existing database. It will also appear in the view of a finderscope, providing this has already been aligned with the main scope. The image below shows a new center-balanced design from iOptron, the CEM40. All of the objects in your current observable sky can be thought of as “projections” on the inside surface of the celestial sphere. Based on the success of iEQ30 mount, the iEQ30 Pro mount uses high resolution, low noise stepper motor to offer better GOTO and tracking accuracy. When the telescope is able to secure a target in place for hours at a time, you can then attach your camera and collect several long exposure images. Equatorial mounts usually require a 2 or 3-star alignment routine to effectively “train” the mount, and is done after a successful polar alignment. When an equatorial telescope mount is parallel to the Earth’s rotational axis, the sky’s apparent motion from east to west can be followed (tracked) accurately. Plate-solving is a popular alternative to a star alignment routine used by amateur and professional astronomers and astrophotographers. On the other hand, the German equatorial mount design has a right ascension (RA)  axis, a declination axis (DEC), and a polar axis (the RA axis aligned with the celestial pole). The telescope is placed on the DEC axis, with a counterweight attached at a balanced position on the other end. They connect to the telescope mount only one way so I won’t cover their attachment procedure. Not only does a GoTo telescope mount make locating objects in the night sky easier, but it also allows you to take long-exposure images (without star trailing). Some of my favorite mounts I’ve ever used for astrophotography are the iOptron CEM60 and the Sky-Watcher EQ6-R Pro. This is a practical method of plotting objects in space using the equatorial coordinate system. The equatorial mount comes in two varieties: German equatorial mount - shaped like a "T." The long axis of the "T" is aligned with the Earth's pole. The equatorial (EQ) mount head is fastened to a tripod that elevates the telescope to a practical height for observations or photography. Now adjust the angle of the polar axis. The tripod should be sturdy and level to provide a stable foundation. This ‘How to’ originally appeared in the January 2014 issue of BBC Sky at Night Magazine. Deep sky astrophotography images captured on an equatorial telescope mount. Certain telescope positions are more susceptible to this possibility than others, such as when the telescope is pointed upwards towards the zenith (the point of the celestial sphere directly overhead of the observer). You’ll find that each company has their own system, but they are all quite similar. Once you’ve worked out your magnetic variance, use a compass to offset the mount as necessary. The QHY PoleMaster electronic polar scope requires an adapter to attach to the telescope mount. A manual equatorial mount will give you dual slow-motion controls in the RA and DEC axis, that you control by slowly turning the knobs on the mount. If it does not, turn the finder’s adjustment screws to achieve alignment. Hold the template and spirit level against the side of the mount’s polar axis as above; you many need to cut a space in the template for your mount’s wormwheel. Both of these mount designs are extremely popular in the amateur astronomy community, and allow the use to freely point the telescope in two perpendicular directions (called axes).

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